Vertically mounted rotary pumps



P 1967 A. s. MALLOCH ETAL 3,339,491

VERTICALLY MOUNTED ROTARY PUMPS Filed July 14, 1965 3 Sheets-Sheet 1 Sept. 5, 1967 A s. MALLOCH ETAL 3,339,491

VERTICALLY MOUNTED ROTARY PUMPS Filed July 14, 1965 I 5 Sheets-Sheet 2 United States Patent M 3,339,491 VERTICALLY MOUNTED ROTARY PUMPS Alexander Stirling Malloch and James Foulds Noble,

Newark, England, assignors to Worthington-Simpson Limited, Newark, England, a British company Filed July 14, 1965, Ser. No. 471,936 Claims priority, application Great Britain, July 17, 1964, 29,232/ 64 6 Claims. (Cl. 103-111) ABSTRACT OF THE DISCLOSURE A rotary machine for handling aggressive liquids including a rotor shaft, a lower sealing chamber and the pumping chamber in communication with the lower sealing chamber, an upper sealing chamber above the lower sealing chamber and having a common wall therebetween, a rotor shaft extending through said sealing chambers and into said pumping chamber, an impeller on the shaft for pressurizing liquid in the pumping chambers, a mechanical seal surrounding the rotor shaft and engaging the common wall in the upper chamber, a sealing liquid in the upper chamber about the mechanical seal, gaseous means communicating with the upper and lower chambers whereby flow from the pumping chamber into the lower sealing chamber is restricted by the gas pressure applied on the aggressive liquid by said gaseous means, and means for releasing gas pressure in the lower chamber at a preselected value.

This invention relates to rotary machines such as pumps, agitators, mixers and stirrers of the kind which are intended to pump or otherwise handle aggressive liquids of either severely corrosive nature or containing abrasive particles. The invention is however more especially concerned with vertically mounted rotary pumps particularly of centrifugal type.

The invention has been devised with the general object of providing an improved rotary machine of the character referred to wherein for the avoidance of wear and deterioration, and in contrast with known machines, no bearing or sealing means is exposed to the liquid which is being handled.

The invention accordingly consists in a rotary machine of the kind referred to comprising a chamber having a gas space situated between the machine rotor and a rotor shaft sealing device and containing the liquid which is being handled and a gas admitted under pressure from an external source for the purpose of maintaining the level of the liquid below the shaft sealing means. When the rotary machine is a pump the liquid is admitted to the chamber at pump suction pressure, or alternatively, if desired, at a pressure intermediate pump suction pressure and pump delivery pressure. The gas may be air or an inert gas depending on the nature of the liquid to be pumped.

In order to regulate the inlet and exhaust of the gas from the external source under different conditions of operation of the rotary machine, for instance in a pump to compensate for any variations in pumping pressures there may be associated with the rotary machine a liquid chamber containing a float or other means coupled to a valve or the equivalent on the gas supply source.

Above the gas chamber the sealing means conveniently consists of a double mechanical seal contained in a separate casing which is connected by feed and return pipes to a reservoir situated above the casing. This system contains oil or other suitable liquid with the reservoir about 75% filled. There is a pipe leading from the gas cham- 3,339,491 Patented Sept. 5, 1967 her to the top of the reservoir for the purpose of ensuring less than that of the gas chamber.

Preferably the double mechanical seal referred to above embodies a spring carrier which is integral with an axial flow helical rotor fitting closely inside the casing and rotating with the pump impeller so as to promote circulation of the sealing liquid round the circuit.

One particular and at present preferred embodiment of the invention and modifications thereof incorporated in a vertically mounted centrifugal pump are illustrated in the accompanying drawings in which:

FIGURE 1 is a vertical section through the pump;

FIGURE 2 shows a level regulating device;

FIGURE 3 shows another sealing device; and

FIGURE 4 shows a modification of the pump which is shown in FIGURE 1.

Referring firstly to FIGURE 1, the centrifugal pump therein shown comprises a multi-part casing having a pumping chamber C, an inlet 10 to be connected to a liquid containing vessel and an outlet 11. An impeller 12 mounted at the lower end of a shaft 13 is located in the pumping chamber and the shaft is coupled to co-axial drive shaft 14 of an elevated electric driving motor 15.

The pump casing incorporates a lower sealing chamber 1 and an upper sealing chamber 5, the latter containing an annular double mechanical sealing unit 16 which surrounds the shaft 13 and engages common wall W between the chambers.

As shown, the liquid which is being pumped has access to the lower chamber 1 because the shaft 13 is not sealed therewith and the level of liquid in this chamber is maintained constant by the admission thereto of a minimal quantity of inert gas at a higher pressure than the liquid through a pipe 17 fitted with a regulating valve 2. The inert gas may be nitrogen or any other gas which is compatible with the liquid which is being pumped and is effective to depress the liquid to the level of a vent 3 in the chamber wall. The gas can escape through this vent which is connected by a pipe 18 to the space above the liquid in the vessel 4, or to a suitable exhaust 37 such as a flare pipe.

The admission of the inert gas to the chamber 1 via the annular clearance space 19 which surrounds the shaft 13 is elfective to afford the maximum amount of protection against seepage of corrosive vapors into the upper chamber 5 which could otherwise damage the mechanical seal.

The upper chamber 5 contains, as shown, a quantity of a separate sealing fluid suflicient to cover the mechanical sealing device 16. The sealing fluid may be oil or other liquid which is compatible with the particular aggressive liquid which is being handled by the pump so that any contamination from sealing fluid leaking through the seal does not have any serious results.

In the top of the chamber 5 is an inlet 6 which is for the purpose of admitting gas to the chamber 5 to ensure that the sealing fluid pressure therein always exceeds the pressure in the chamber 1.

An alternative arrangement for controlling the liquid level in chamber 1 is by means of a level regulating device such as that shown in FIGURE 2. This device comprises a tank 22 which would be bolted onto the side of the chamber 1 and communicates therewith so as also to contain the liquid which is being pumped and the inert gas by which the liquid level is regulated.

The tank 22 contains a float 23 mounted on a curved arm 24 which is pivotally connected to the tank and may be adapted to control admission or exhaust or as is shown in FIGURE 2, both to admit and exhaust inert gas by operating an inert gas supply valve 25 and inert gas release valve 26. The supply valve 25 admits inert gas via an intermediate chamber 27 through pipe 28 to pipe 17 (FIG. 1) regulating valve 2 and escape vent 3 then being absent.

FIGURE 3 shows an alternative sealing arrangement substituted for the upper chamber 5 and seal 16 shown. It consists of a double mechanical seal contained in a close fitted housing 7 and connected by inlet and outlet pipes 29, 30 respectively to a separate sealing liquid reservoir 8 situated above the upper chamber. The whole system is filled with sealing liquid to about 75% of the capacity of the reservoir which is connected to a gas supply pipe 31. Gas may be supplied through this pipe from a direct high pressure gas source or if preferred from the top of the liquid-gas chamber 1 of the pump.

The carrier 9 for the mechanical seal spring 32 is formed externally with a helical groove or grooves 9a so as to act on rotation as an axial screw pump and thereby promote positive circulation of the sealing liquid around the circuit as well as imposing some additional pressure on the seal between the chambers 7 and 1. An advantage of the positive circulation due to the screw pump carrier 9 is that when very hot liquids are being pumped, a heat exchanger 33 can be incorporated in a return pipe from the mechanical seal to the reservoir 8.

In the arrangement shown in FIGURE 1 there are no internal bearings within the pump casing or the gas-liquid chamber 1, the impeller 12 being carried on an extra stiff shaft 13 suported in two external anti-friction bearings 34 which are never in contact with the pumped liquid. The motor 15 is of a separate standard type and its drive shaft 14 is connected to impeller shaft 13 by a flexible coupling 35.

In FIGURE 4 there is shown an alternative structure corresponding parts bear the same reference numerals except they are primed. In this embodiment in which there is a unitary motor-impeller shaft 36 is operably coupled to the motor 151 thus eliminating intermediate bearings and reducing the overall axial length of the pump as well as its cost.

In addition, it will be noted that the upper chamber 5' is provided with an inlet 6a connected via a pipe 20 to a vent 21 in the upper portion of the chamber 1. By virtue of the static head of sealing fluid in the chamber 5', this ensures that the sealing fluid pressure in the chamber 5' exceeds the gas liquid pressure in the chamber 1'.

We claim:

1. A rotary machine for handling aggressive liquids comprising a rotor shaft, means defining a lower sealing chamber and a pumping chamber in communication with said lower sealing chamber, means defining an upper sealing chamber above said lower sealing chamber and having a common wall therebetween, said rotor shaft extending through said chambers and into said pumping chamber, an impeller on said rotor shaft for pressurizing liquids in said pumping chamber, a mechanical seal about said rotor shaft and engaging said common wall located in said upper chamber, a sealing liquid in said upper chamber about said mechanical seal, gaseous means communicating with said upper and lower chambers whereby flow from said pumping chamber into said lower sealing chamber is restricted by the gas pressure applied on the aggressive liquid by said gaseous means, and means for releasing gas pressure in said lower chamber at a preselected value.

2. The rotary machine as claimed in claim 1 in which said gas means for releasing gas pressure includes a device responsive to changes of liquid level in said lower chamber.

3. A rotary machine as claimed in claim 2 in which said device includes a tank communicating with said lower chamber, and gas admission and exhaust valve means therefor with said gaseous means operating said admission and exhaust valve means.

4. The rotary machine as claimed in claim 1 in which said means defining said lower sealing chamber is provided with an annulus surrounding said rotary shaft and through which annulus said gaseous means communicates with said lower chamber.

5. The rotary machine as claimed in claim 1 including a separate sealing liquid reservoir located above the level of said mechanical seal, and inlet and outlet conduit means located between said reservoir and said mechanical seal. a

6. A vertical centrifugal pump for handling aggressive liquids comprising a shaft, means defining a lower sealing chamber and a pumping chamber in communication with said lower sealing chamber, means defining an upper sealing chamber above said lower sealing chamber and having a common wall therebetween, said shaft extending through said chambers and into said pumping chamber, an impeller on said shaft for pressurizing liquids in said pumping chamber, a mechanical seal about said shaft and engaging said common wall located in said upper chamber, a sealing liquid in said upper chamber about said mechanical seal, gaseous means communicating with said upper and lower chambers whereby flow from said pumping chamber into said lower sealing chamber is restricted by the gas pressure applied on the aggressive liquid gaseous means, and means for releasing gas pressure in said lower chamber at said pre-selected value.

References Cited UNITED STATES PATENTS 2,075,895 4/1937 Harmon 103-111 2,423,825 9/1947 Blom 1031 11 2,911,919 11/1959 Tucker 103111 2,935,026 5/1960 .Abramson 103111 2,949,321 8/1960 Tracy 1031 11 2,959,133 11/1960 Erwin 103111 3,048,118 8/1962 Erd 103111 FOREIGN PATENTS 788,831 1/1958 Great Britain. 557,753 2/ 1957 Italy.

DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. A ROTARY MACHINE FOR HANDLING AGGRESSIVE LIQUIDS COMPRISING A ROTOR SHAFT, MEANS DEFINING A LOWER SEALING CHAMBER AND A PUMPING CHAMBER IN COMMUNICATION WITH SAID LOWER SEALING CHAMBER, MEANS DEFINING AN UPPER SEALING CHAMBER ABOVE SAID LOWER SEALING CHAMBER AND HAVING A COMMON WALL THEREBETWEEN, SAID ROTOR SHAFT EXTENDING THROUGH SAID CHAMBERS AND INTO SAID PUMPING CHAMBER, AN IMPELLER ON SAID ROTOR SHAFT FOR PRESSURIZING LIQUIDS IN SAID PUMPING CHAMBER, A MECHANICAL SEAL ABOUT SAID ROTOR SHAFT AND ENGAGING SAID COMMON WALL LOCATED IN SAID UPPER CHAMBER, A SEALING LIQUID IN SAID UPPER CHAMBER ABOUT UPPER MECHANICAL SEAL, GASEOUS MEANS COMMUNICATING WITH SAID UPPER AND LOWER CHAMBERS WHEREBY 